The proposed studies will deal with the developmental, structural and immunological aspects of the Rh antigen content of the human red cell. The major purpose of the project is to elucidate the biological role of the Rh antigen complex in maintaining the structural and functional integrity of the red cell in health and in hemolytic states. Radioisotope-labeled antibodies in the Rh antigen, electron microscopy using ferritin-conjugated antibodies and autoradiography are some of the techniques that will be used. An important component of these studies will deal with the isolation and chemical characterization of the Rh antigens obtained from solubilized red cell membranes.